1. Field of the Invention
This invention relates to the field of fire sensors generally, and in particular, to fire sensors using microprocessors instead of discrete analog circuits to determine whether a fire exists.
2. Background of the Invention
There presently exist many techniques for sensing the presence of fires or explosions within a protected area, and for discriminating against other phenomena that create false alarms. Some examples of phenomena which fire sensors discriminate against include sunlight, small fires, explosions which do not cause a fire, and the flash created by a projectile piercing a wall of the protected area. Previous discrimination techniques use various combinations of spectral selection and various comparisons between the sensed energy of the various spectral regions. Prior art discrimination techniques have employed discrete analog circuitry, such as op-amps and comparators, in conjunction with a few digital gates. Such discrimination circuits have been kept intentionally simple because the fire sensor packages must remain small and light to be useful. Complex circuitry also increases the selling price of the fire sensor. It would be advantageous to obtain a fire sensor that is light, small, and inexpensive while still being able to perform relatively complex analysis of the radiation sensed. It would also be desirable to realize the discrimination circuitry in a form wherein the discrimination techniques could be readily changed without discarding or changing the actual hardware. Such advantages have not been obtainable with prior art fire sensors.